1. Field of the Invention
The present invention relates to a continuous two-liquid type mixer for mixing two liquid materials, more particularly, it relates to a mixer capable of mixing quickly and uniformly two kinds of liquids such as liquid synthetic resins, solvents, curing agents and the like.
2. Description of the Prior Art
As materials for moldings such as synthetic resin films and synthetic resin sheets, synethetic resins of reactive curing type are often used, and examples of reactive curing type synthetic resins are polymide resin, epoxy resin, urethane resin, phenol resin, unsaturated polyester resin and the like.
Synthetic resins of the reactive curing type are known to be of two-liquid type and, when the two liquid components, such as a resin component and a curing component, are mixed, the viscosity of the mixture starts rising (curing starts) and continues rising until the mixture is no longer moldable. When a synthetic resin becomes unmoldable it reaches the end of its "pot life," and this pot life depends on the ambient temperature and the ratio of the two liquid components mixed together. Hence, when mixing of the two liquid components is not uniform, that is, when, for example, the concentration of the curing component is locally too high, such part is cured quickly a resulting in a state in which the cured or hardened portion of the resin remains suspended locally in the uncured portion. Even if mixing of the two liquid components is done uniformly, it is often possible that the pot life expires as the mixture remains in the mixer or locally quicker progress of curing takes place, which may possibly result in the coexistence of liquid mixtures having different properties.
If there are some portions which are advanced in the degree of curing in a mixed resinous liquid, they are likely to appear on the surface of a synthetic resin molding as foreign objects, or cause deterioration of the properties of molded articles, hence the mixer is required to be capable of mixing the two liquids uniformly and quickly, at the same time preventing dwelling of the mixed liquid in the mixer.
As such a mixer there is known one with both stationary and rotary impellers designed so that a resinous liquid flows through the liquid inlet toward the outlet of a cylindrical container, while the curing agent is fed in through a liquid inlet provided in the side wall of the cylindrical container so that the resin and the curing agent are mixed together continuously.
In this conventional device, the two liquids can be mixed together easily and uniformly if there is no difference in viscosities between them. However--, mixing is not easy if there is any sizable difference between a resin with its viscosity of several thousands poises and a curing agent whose viscosity ranges from several poises to several 10.sup.-3 poises. In such instances and the curing agent injected through the peripheral wall of the cylindrical container is caused to flow along its inside, sandwiched between layers of the resin to a given extent, and being mixed with the resin gradually. In the predetermined range the concentration of the curing agent remains high, hence the curing is enhanced locally, this giving rise to the aforementioned problem. Meanwhile, increasing the rotary stirring blade's speed in order to enhance mixing, the temperature of the solution rises due to generation of Joule's heat et cetera, resulting in a shorter pot life.